An additional idea would be to have a "Frequent" flyout box similar to NRST, where iFly keeps a weighted list of my most-used airports. That would help me, as I frequent a lot of the same airports. It could also benefit renters who fly out of multiple airports.
I agree - actually, the previous navigation software I used also had a short list of "Favorites". This popped up alongside the identifier entry area and you could just tap the "Favorite" airport's identifier and it was entered with that one tap. If I recall correctly the Favorite list was gradually built up by the program without user intervention - it arranged the list from the frequency you entered a particular airport, so obviously your home base was at the top of the list.
John